The expression “microwave-assisted chemical reactions” as used herein refers to processes utilizing microwaves to initiate or accelerate chemical reactions. Microwave-assisted chemistry is used for heating materials in a variety of chemical processes, the microwaves interacting directly with the materials including water and a number of organic liquids to cause molecular action and generate heat. Accordingly, microwave-assisted techniques have been developed both for analytic and synthetic processes. The equipment used for performing microwave-assisted chemistry conventionally includes an apparatus having a cavity into which microwaves are guided from a microwave source, typically a magnetron. A vessel, containing the reactants, is introduced in the cavity and positioned for exposure to the microwaves. In some appliances, the vessel is a sealed container in which a reaction can proceed under conditions of both elevated temperature and elevated pressure. The vessel, and the apparatus for exposing the reaction mixture in the vessel to microwaves, provide the basic components in a system for performing microwave-assisted chemical reactions. In commercial practice, the system additionally comprises means for vessel transport to and from the cavity, means for dispensing solvent and reactants to the vessel, detection means, power and control means, and a rack for parking the vessel outside the cavity.
A commercially available reaction vessel in a system for performing microwave-assisted chemical reactions is diagrammatically shown in FIG. 1 of the drawings, attached hereto. This known reaction vessel comprises the well known shape of a test tube, having a penetrable septum capped over the open end of the tube. The tube diameter is dimensioned to fit with other components of the system such as the cavity entrance, gripper means and a parking rack. The vessel has a reaction chamber dimensioned for containment of reaction mixture volumes commonly processed in the system.
In this context, the expression “small reaction mixture volumes” refers to reaction mixture volumes in a micro liter range, such as volumes down to 500 μl or less, for example 1-500 μl, preferably 100-500 μl. Specific problems need to be addressed when designing a reaction vessel for performing microwave-assisted chemistry on small volumes contained in the vessel. For example, the geometry in a top portion of the vessel should be designed to facilitate reflux/re-flow of fluid; the inner diameter of the vessel should be large enough to avoid formation of meniscus of fluid that would be unable to flow back from the top of the vessel; the container volume that is not occupied by the reaction mixture, or head space, should be related to the volume of reactants to avoid exaggerated vaporization at operative pressures and temperatures; in spite of reduced containment dimensions, the vessel exterior must match the cavity entrance diameter and the transporting gripper means, as well as parking racks, and the vessel must be able to position the reaction mixture for dispensing of reactants and/or solvents, for microwave exposure, and for detection.
The present invention aims to solve these and other problems encountered when performing microwave-assisted chemical reactions on small volumes.
A first object of the invention is therefore to provide a micro vial assembly that allows microwave-assisted chemistry to be performed on small volumes.
Another object is to provide a micro vial assembly for performing microwave-assisted chemistry on small volumes, adapted for cooperation with external equipment designed for microwave-assisted chemistry on a larger scale.
Still another object is to provide -a micro vial assembly for performing microwave-assisted chemistry on small volumes, designed to ensure comparative temperature and pressure detection results.
Yet another object is to provide a system that allows microwave-assisted chemistry to be performed on small volumes by incorporating the micro vial assembly of the invention.
These and other objects and aims are met in a micro vial assembly and a system according to the appended claims.